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Designation: D5391 − 14Standard Test Method forElectrical Conductivity and Resistivity of a Flowing HighPurity Water Sample 1This standard is issued under the f i xed designation D5391; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (´) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the determination of electricalconductivity and resistivity of high purity water samples below10 µS/cm (above 0.1 Mohm-cm). It is applicable to bothcontinuous and periodic measurements but in all cases, thewater must be f l owing in order to provide representativesampling. Static grab sampling cannot be used for such highpurity water. Continuous measurements are made directly inpure water process lines, or in side stream sample lines toenable measurements on high temperature or high pressuresamples, or both.1.2 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards: 2D1066 Practice for Sampling SteamD1125 Test Methods for Electrical Conductivity and Resis-tivity of WaterD1129 Terminology Relating to WaterD1192 Guide for Equipment for Sampling Water and Steamin Closed Conduits (Withdrawn 2003) 3D1193 Specif i cation for Reagent WaterD2186 Test Methods for Deposit-Forming Impurities inSteamD2777 Practice for Determination of Precision and Bias ofApplicable Test Methods of Committee D19 on WaterD3370 Practices for Sampling Water from Closed ConduitsD3864 Guide for On-Line Monitoring Systems for WaterAnalysisD4519 Test Method for On-Line Determination of Anionsand Carbon Dioxide in High Purity Water by CationExchange and Degassed Cation Conductivity3. Terminology3.1 Def i nitions—For def i nitions of other terms used in thesetest methods, refer to Terminology D1129.3.1.1 electrical conductivity—refer to Test Methods D1125.3.1.2 electrical resistivity—refer to Test Methods D1125.3.2 Def i nitions of Terms Specif i c to This Standard:3.2.1 cell constant, n—the ratio of the length of the path, L(cm), and the cross-sectional area of the solution, A (cm 2 ),between the electrodes of a conductivity/resistivity cell, withunits of cm −1 .3.2.1.1 Discussion—In high purity water measurements, thecell constant is normally between 0.001 and 0.1 cm −1 toprevent electrical interference. This is lower than the 1 cm −1 ofthe standard centimetre cube and is taken into account by directreading instrument ranges that are matched with specif i c cellconstants.4. Summary of Test Method4.1 Conductivity or resistivity is measured with a cell andtemperature sensor or compensator in a f l owing, closed systemto prevent trace contamination from wetted surfaces and fromthe atmosphere. Specialized temperature compensation cor-rects the measurement to 25°C, taking into account thetemperature effects on the ionization of water, thecontaminants, and interactions between the two. In the absenceof specialized temperature compensation, the sample tempera-ture is controlled to 25 6 0.2°C.4.2 To determine the cell constant of a high purity conduc-tivity cell with an instrument capable of accurate measurementover the range of pure water to 150 µS/cm with a single cell1 This test method is under the jurisdiction of ASTM Committee D19 on Waterand is the direct responsibility of Subcommittee D19.03 on Sampling Water andWater-Formed Deposits, Analysis of Water for Power Generation and Process Use,On-Line Water Analysis, and Surveillance of Water.Current edition approved Feb. 1, 2014. Published February 2014. Originallyapproved in 1993. Last previous edition approved in 2009 as D5391 – 99 (2009).DOI: 10.1520/D5391-14.2 For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at service@astm.org. For Annual Book of ASTMStandards volume information, refer to the standard’s Document Summary page onthe ASTM website.3 The last approved version of this historical standard is referenced onwww.astm.org.Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.1